The Ford specifications said that the 1963 stock Challenger 260 V-8 delivered 258 ft-lbs of torque at 2200 rpm and 165 hp at 4400 rpm. The red-line was 5000 rpm.

I have a Hot Rod Magazine, dated October 1963, that describes how Carroll Shelby dyno-tested a stock 260 engine and obtained the following results. (I added the equivalent mph after the rpm for a 3.25 rear end, 13" wheels, and a 1:1 transmission). Shelby's 260 only developed 141 hp versus Ford's claimed 164 hp. The article is called: "200 HP Cobra Dealer Bolt-On for Falcon V-8".

What I found amazing is that the stock engine was making 137 hp (97% of the peak 141) at only 3500 rpm and added just another 4 hp by revving 1000 rpm faster. The engine delivers nearly its full power at a usable speed (77 mph) while not breaking a sweat and at a full 1500 rpm below red-line.